Design and characterization of microfabricated piezoresistive floating element-based shear stress sensors

This paper presents the design, fabrication, and characterization of unique piezoresistive microfabricated shear stress sensors for direct measurements of shear stress underwater. Sidewall-implanted piezoresistors measure lateral force (integrated shear stress) and traditional top-implanted piezores...

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Bibliographic Details
Published in:Sensors and actuators. A. Physical. 2007-02, Vol.134 (1), p.77-87
Main Authors: Barlian, A. Alvin, Park, Sung-Jin, Mukundan, Vikram, Pruitt, Beth L.
Format: Article
Language:English
Subjects:
Floating element
In-plane force
Ion implantation
MEMS
Micromachined
Oblique-implant
Out-of-plane force
Piezoresistive
Piezoresistors
Shear stress sensor
Underwater
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Summary:This paper presents the design, fabrication, and characterization of unique piezoresistive microfabricated shear stress sensors for direct measurements of shear stress underwater. Sidewall-implanted piezoresistors measure lateral force (integrated shear stress) and traditional top-implanted piezoresistors detect normal forces. In addition to the oblique-implant technique, the fabrication process includes a hydrogen anneal step to smooth scalloped silicon sidewalls left by the deep reactive ion etch (DRIE) process. This step was found to reduce the 1/ f noise level by almost an order of magnitude for the sidewall-implanted piezoresistors. Lateral sensitivity was characterized using a microfabricated silicon cantilever force sensor. Out-of-plane sensitivity was evaluated by laser Doppler vibrometry and resonance of the plate element. In-plane sensitivity and out-of-plane crosstalk were characterized, as well as hysteresis and repeatability of the measurements. TSUPREM-4 simulations were used to investigate the discrepancies between the theoretical and experimental values of sidewall-implanted piezoresistor sensitivity. The sensors are designed to be used underwater for studies of hydrodynamic flows.
ISSN:0924-4247
1873-3069
DOI:10.1016/j.sna.2006.04.035